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WASHINGTON (CNN) -- A portion of a controversial Texas congressional map was tossed out Wednesday by the Supreme Court, but the overall redistricting plan engineered by state Republicans was found to be proper.

The fractured decision represents partial victories for the state GOP and for civil rights and minority voter groups opposed to the map.

The legislative plan led to the 2004 ouster of four Democratic incumbents from Congress, and sparked a bitter partisan battle. The map was was promoted by Republicans, including former majority leader Rep. Tom DeLay.

The divided ruling concluded that a congressional district unfairly weakened the voting strength of Latinos in two congressional districts in the western part of the state. (Read the court's redistricting opinion)

"A state may not trade off the rights of some members of a racial group against the rights of other members of that group," wrote Justice Anthony Kennedy for the majority. "The question is therefore not whether line-drawing in the challenged area as a whole dilutes minority voting strength, but whether line-drawing dilutes the voting strength of the Latinos in District 23." The Court concluded that District 23 violated the Voting Rights Act, while nearby District 25 was found to be valid.

Court: Map not overly partisan

At issue was whether courts can fashion a proper remedy when partisan gerrymandering is judged excessive, and whether states can remake their congressional map when a valid plan already exists based on that decade's census numbers.

Taken as a whole, the Court rejected arguments that the Texas congressional map was an overly partisan attempt to push out Democratic incumbents in Congress, known as gerrymandering.

"The text and structure of the Constitution and our case law indicate there is nothing inherently suspect about a legislature's decision to replace mid-decade a court-ordered plan with one of its own," the ruling said.

The justices ordered lower courts and the state to fashion a new District 23. The district takes up a huge part of west Texas, from El Paso to San Antonio, and the seat is held by Rep. Henry Bonilla, a seven-term Republican.

It is unclear whether a new map for District 23 can be redrawn in time for the November midterm elections.

District 25 runs from Austin to the Texas border, and Justice Steven Breyer, during oral arguments, likened it to a "long walking stick." Democrat Lloyd Doggett has held that seat for six terms.

Texas Solicitor General Ted Cruz told the court the 2003 map was an effort to correct the fact that although the majority of Texas voters were Republicans, Democrats had a two-seat majority in the state's congressional delegation.

A DeLay-backed plan

Following constitutional mandate, states are required to redraw their congressional districts every 10 years, in line with population changes. After the 2000 census, a state court redrew the Texas map with input from state lawmakers. But after DeLay helped Republicans gain control of the state legislature in 2002, he promoted a second redistricting proposal for congressional boundaries.

The Texas legislature adopted the plan in 2003 after three contentious special sessions called by Republican Gov. Rick Perry. Angry Democratic legislators left the sessions twice en masse, denying the GOP a quorum to proceed. DeLay ultimately helped negotiate a redistricting plan that won approval but was quickly challenged in court by Democrats and several minority rights groups.

The newly drawn districts helped Republicans gain a majority of the state's 32 congressional seats. Before the 2004 elections, the GOP held 15 seats; it now has 21. Opponents challenging the redistricting plan alleged it moved 8 million people into new districts, and relied on inaccurate census data.

Republicans countered the plan was a legitimate exercise in legislative authority, and the changes led to the 2004 election of a Democratic African-American, Rep. Gene Green, who joined African-Americans Eddie Bernice Johnson and Sheila Jackson Lee in the Texas congressional delegation.

Kennedy again the swing vote

Kennedy proved to be the key swing vote in the complex case. Five separate opinions were issued, in which various coalitions agreed or disagreed with various parts of the legal challenges.

Kennedy had agreed with a 5-4 majority that restricted challenges to Pennsylvania's Republican-drawn congressional map. But Kennedy at the time separately offered opponents of political gerrymandering some hope of making their case, noting he might reconsider his views if he could find "some limited and precise rationale ... to correct an established violation of the Constitution."

In the Texas case, the 69-year-old justice apparently did not see enough to change his mind. "A congressional plan that more closely reflects the distribution of state party power seems a less likely vehicle for partisan discrimination than one that entrenches an electoral minority," he wrote of the over Texas map.

Dissenting in part, Justice John Paul Stevens noted, "Whether a districting map is biased against a political party depends upon bias in the map itself -- in other words, it depends upon the opportunities that the map offers each party, regardless of how candidates perform in a given year."

He said the Texas plan pushed by Republicans "has a discriminatory effect in terms of the opportunities it offers the two principal parties in Texas. Indeed, that discriminatory effect is severe."

Hispanics vow vigilance

Hispanic voting groups promised to watch the process for redrawing District 23 closely.

"The federal courts have to come in and protect the rights of Latinos against the abuses of the state of Texas," Rolando Rios, an attorney in the case, told CNN. Rios said Perry, DeLay and the GOP in Texas "do everything they can to keep us from having our due" in congressional representation.

There is precedent for judicial intervention in such cases. The Supreme Court in 1996 upheld a ruling that found three congressional Texas districts were improperly drawn, leading to new boundaries and a November primary, followed by a election runoff a month later.

DeLay represented a Houston-area district, but stepped down this month from his House seat after his October indictment on money laundering charges, which he has denied.

The Texas cases could have enormous short- and long-term implications. Georgia and Colorado also have adopted a second round of congressional redistricting.